Generator coupling circuit



Nov. 3, 1953 J. E. EVANS EI'AL FIG/l I MAGNETRON'W t-L so +1 MAGNETRON2.

OUTPUT TO MAGNETRON'I 1 TO MAGNETRON *2 4 PULSE CABLE FROM MODULATORFIG. 2

K To MAGNETRON ALTERNATING VOLTAGE 3 J SOURGL 1 3 l5 R.F. OUTPUT j"MAGNETRONQ R'.EOUTPUT INVENTORS JOHN E. EVANS FOSTER F. RIEKE PatentedNov. 3,

PATENT orrlcs s1gnmen e 1 9 States o lh ti e a the etary 9? We?pplication February 18, 1946, Serial No. 648,523 5 Lihh (c1; itt -hi5).

This invention relates in general to tunable electronic oscillatorcircuits, and more particu,- larly to such circuits ad pted to operatein th centimeter wavelength ran e.

As the design of electronic oscillators has evolved so that higher andhigher frequencies of oscillations can be generated, the size andspacing of the elements within the thermionic tubes contained in suchcircuits, in eneral have. become smaller and smaller. In a few specificmea s the dime s ns f th tub lem and/or the distances between tubeelements may be ar e; 1. e, of the lar r of a Wa el n h. The lattertubes must-have these dim n iqns, a p rcen e s of a Wavele th careful ychose In e al, owever, it ma he sa d th t the t es a p d f r thegeheration 9f hy e q n ies ha less power hamll n cap cit han tube i ed fr use mills-10W req ency vran e, ecause he mo hte snewer a tube ca hndle i e ned o a a roximation by the amount of power dissipating surfacearea there is inassc t n therew th h eiq e i h h Power i des red i thecent me r a e resign a tube a the m e r .o r ins nce, hmt i eneral totuhes it lareerpremg e massive elements e use he size si tth e htsthatwphhl' he desired for Proner at $391. uld h in n lic i h h .A. f thee e .S ne es ar for P p r hh at th high ireqhent rah es asstipulatedapgve,

A on the hosts the present hvehtiqn, therefore, are:

To d ah =9$il %l 5 thermihhit tube a -w r he e amen fih re t t ueh iesl'efei ablya ma'snetto .ahd'

TO p viti 111 1 1 't t it emhqq i tuhes wherein relatively-large amountsof power are generated, it o In tt m ntwiththehre ehtih eht qh that? a pvide two m e t qh nestle v th eh h Wave guides to a ist ce be een th eaq'maehe tive parallel resona the circuit will be after in this speci Th in i n s anc to the h? F 1 -o .ta ,t.ee V

n a parallel his 2 is .a. -now er v distr.ihution ,circuitior the stemof the twopara lel ima net ons; and

Fig. 3 is a cross sectional view of a type of 1 tion of t 2 couplingmeans which could b u ed h the Pi t ent system.

' Referring now to a. description of the invention and ti! Fig. 1, therei Shown a circuit diagram which, With th p op len ths f in a e-shobetween h a l l re hah cir uits and the output i e ma he made to he eltr eelly qu va ent 9 h system 9f the nr seh h t f tio Inth s iaeramthemehetmhs e ethhhthi or as-act ns as pa allel res na t circuits u a certainlen th Lot transmiss line,- v f his. 21s a circuit d a ra oi one t pe 9fnew r dis ribution s stem hat ma h ezhhlq efi f the tw ma n on-s #1 the#2- lhe zi 5f the tub s. a e p ced at s qhhd 9t ti l Th c eat rs. o thetl htfi hd- Q9??? hhh h fi h m transinrmers 9 a11d H, e p im which a eqehhles to a elit hhi he i source.- If the system 91' in? 91 i latedtype, as is o the case, the pulse mm th med tate? is h .h hl P 9 W whitein aral e Cehhlihs th hills? thl? t th h d .Q #1 s a Pen t n w r f i 1.2and' phhlehssi .31 it an emme er I4 i the resis or brhhqh thiertet L i eh h th ulse ab e .th th heihodeh m h i h is "a paral httwi 1% 9 e s r1'5 hr1111 'th l t r it w th H in he thi h ahththef .of. Fig.3 is across sectional view of a T- junction hich ma he use? t .teih heth p' ten e from th W9 m hehehe ."M l t s upled o Q 1 9w l hi hr h'lfl' t T-iuhr tion, while magnetron #2 is coupled to the. other w ve uide h t hthzlirth p h shhi trac he ene y th th h we guides a ccexia l ner? is ha s h'd mid-w r e ten the woae sh h i 99th the are mm tr l: The bet e tehsiuce '91 the eq xh h s ai ed m cha t l a ts en .h a t su 23. The effectivelength of this stub' is a quarter of a wavelen th at he repeat n e e t?s n et e thhh 9 3'.?; l n hd t re i a hi h mpedanc 99m in o the stab a h1 4 ti o the stub h th W v hidh l ds the stub a ve li e 9 9 th le q a twaves i th .sys erh- Refe ri newto a fle r i h .Qith 116 v. s temahdts.- hit s 11 2 W! he a m ro te ethe w t ho h t electrical-lyas ifit-Were a parallel r sonant circui and a ertain enethh 9 ,teh m h i eThat is, the circuit to the lett of the Idotted 11 12391 qhsicleted tolth ihe het trical eduivalentof a magnetron as seen from aoeaics theoutside of the coupling means. That is, if an instrument were connectedat the output of the magnetron, this instrument being insensitive toeffects from the direction of the T-junction point of the circuit, andonly be effected by the manner in which the circuit elements on themagnetron #1 side of the dotted line 30 perform, this instrument wouldbe said to see only the characteristics of the circuit to the left ofthis dotted line. A series resonant circuit plus a length oftransmission line could have been chosen for the equivalent circuit ofthe magnetron, in which case the length of line would be a quarter of awavelength different from the length of line in the equivalent circuitof Fig. 1.

It is desirable that the two magnetrons used be of nearly identicalcharacteristics, and that the output couplings of the two tubes haveequal impedance characteristics as far as is possible. For effectiveparallel operation, each magnetron must see the other as a parallelresonant circuit. This will occur if the effective distance between thetwo magnetrons is an integral number of half wavelengths inside the waveguide. It can be seen, however, that since the length of line L is ingeneral unknown, the physical distance between the two tubes must bedetermined by instrumentation. Actually, the lengths of the T arms areso chosen that the frequency of the magnetron is least stable with a menstand-- ing wave ratio in the line when the minimum in the standing wavepattern is at the T. With a constant standing wave ratio in the outputline from the magnetron, as the phase of the standing waves in the lineis varied through 180, the magnetron, besides varying in frequency andoutput power, goes through a region of poor stability to one of goodstability and back again to one of poor. Thus the region in which themagnetron is least stable may be determined from the operatingcharacteristics.

In the diagram in Fig. 1, it is seen that one desirable operatingcondition in which the above requirements would hold is the positioningof the two magnetrons at such a distance apart that the effectiveparallel resonant circuits are an even number of integral half guidewavelengths apart. In this configuration, the oscillations within thetwo tubes would lock in, or synchronize, in phase. It it also possibleto place the two magnetrons at such a distance that these effectiveparallel resonant circuits are an odd number of half guide wavelengthsapart. In this case, the oscillations would synchronize 180 out ofphase.

Due to the circuitry, the load conductance is divided substantiallyequally between the two magnetrons and so, if each magnetron as coupledto its line has a loaded Q equal to QL, the loaded Q of the combinationis 2QL. To obtain good coupling, this value of Q1. should be rathersmall.

In the pulse distributing and monitoring circuit shown in Fig. 2, it isnecessary to have a filament transformer for each magnetron, in orderthat the average current ammeters l4 and I1 read the individualmagnetron currents. These two currents can be adjusted to substantialequality by proper setting of the magnetic fiields for the individualmagnetrons.

In one operation of the system, two so-called "K-l magnetrons were runwith a magnetic field of 1200 gauss and at 12-15 D.-C. amperes each, onthe maximum of the pulse. The radio frequency output had a frequencyspectrum similar to that of a single magnetron, thus showing that thetwo tubes had locked in. It was further found that the tubecharacteristics as a function of load were much the same as those of asingle magnetron. The maximum efficiency obtained was about 38%. If onemagnetron was turned off it was found that the radio frequency powerdropped to about half of its former value.

It will be understood in the interpretation of this specification, thatnot only two but any number of magnetrons may be placed eifecively inparallel in accordance with the principles set forth above. Furthermore,it is seen that there are other types of hyperfrequency oscillatorswhich may be coupled into a common output line utilizing in general theprinciples set down here, it being of course necessary to make slightmodi-- fications with respect to the properties peculiar; to each typeof oscillator used.

While there has been described what is at;

present considered the preferred embodiment of. the invention, it willbe obvious to those skilled. in the art that various changes andmodifications.

may be made therein without departing from.

the invention, and it is, therefore, aimed in the; appended claims tocover all such changes and modifications as fall within the true spiritand. scope of the invention.

What is claimed is:

1. In combination, a plurality of magnetrons: for generating highfrequencies, an output trans-- mission line means, and a plurality ofcon-- necting transmission line means, each of said. connectingtransmission line means coupling one. of said high frequency magnetronsto said out put transmission line, the distance between any. one of saidhigh frequencymagnetrons and any." other of said high frequencymagnetrons as. measured along said connecting transmission. line meansbeing effectively an integral number of half -wavelengths, saidwavelengths being those; occurring within said connecting transmission.line means.

2. In combination, a plurality of oscillating; high frequencyoscillation generators, an output. transmission line, and a plurality ofequal length. coupling transmission lines, each of said cou-- plingtransmission lines connecting one of saidhigh frequency oscillationgenerators to said out-- put transmission line, the distance between anyone of said high frequency oscillation generators; and any other of saidhigh frequency oscillation. generators as measured within said coupling:transmission lines being effectively an integral: number ofhalf-wavelengths as measured at the. operating frequency of the system.

3. In combination, a plurality of magnetrons; for generating highfrequencies, an output transmission line, and a plurality of couplingtransmission lines, each of said coupling transmission lines connectingone of said high frequencymagnetrons to said output transmission line,the: distances between said high frequency magne trons as measured alongsaid coupling transmission lines being effectively an integral number ofhalf-wavelengths as measured at the operating frequency of the system.

4. In combination, a plurality of high frequency generator means, anoutput transmission line means, and a plurality of coupling transmissionline means, each of said coupling transmission line means connecting oneof said high frequency generator means to said output transmission linemeans, the distances between said high frequency generator means asmeas- 5 ured along said coupling transmission line means beingeffectively an integral number of half-wavelengths as measured at theoperating frequency 01' the system.

5. The combination of claim 3, further including a plurality of currentmeasuring means respectively connected to said magnetrons, for measuringthe respective magnetron loading, whereby the effective length of saidcoupling transmission lines may be determined.

JOHN E. EVANS. FOSTER. F. RIEKE.

6 References Cited in the file of this patent UNITED STATES PATENTSNumber Name Date Linder Mar. 8 ,1938 Wolfi Apr. 5, 1938 Schussler Oct.7, 1941 Schonfeld Jan. 20, 1942 Bull Mar. 8, 1949 Everhart June 7, 1949Southworth July 11, 1950

